Methods and devices for electrosurgery

ABSTRACT

Method and devices for electrosurgery by means of oxy-hydro combustion. Deleterious effects to tissue are minimized by means of control of acid-base shift reactions, which reactions can further be employed to control oxy-hydro combustion reactions. In one embodiment, radiofrequency energy in electrical connection with electrodes is employed to induce electrolysis in an aqueous salt environment, thereby producing oxygen and hydrogen, with the same energy source employed to initiate a combustion reaction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing of U.S. ProvisionalPatent Application Ser. No. 60/312,965, entitled System and Method ofElectrosurgical Biologic Tissue Modification and Treatment UtilizingOxy-Hydro Combustion—Acid Base Shift Reactions, filed on Aug. 15, 2001,and the specification thereof is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention (Technical Field)

The present invention relates to methods and devices for electrosurgery,including devices that operate in a conductive media, including anaqueous conductive media, by means of oxygen and hydrogen combustion.

2. Background Art

Note that the following discussion refers to a number of publications byauthor(s) and year of publication, and that due to recent publicationdates certain publications are not to be considered as prior artvis-a-vis the present invention. Discussion of such publications hereinis given for more complete background and is not to be construed as anadmission that such publications are prior art for patentabilitydetermination purposes.

A variety of electrosurgical devices, used for cutting, ablation, andthe like in surgical procedures, are known. In general, it is claimedthat these devices utilize mechanisms of action based on various plasmaformation physiochemical paradigms. A plasma, broadly defined as “thefourth state of matter” as opposed to solids, liquids, and gases, is astate in which atoms have been broken down to form free electrons andstripped nuclei by the application of high energy or temperatures (ca.10⁶ degrees). In a plasma, the charge of the electrons is balanced bythe charge of the positive ions so that the system as a whole iselectrically neutral. The energy input required to initiate a plasma isrelated to the initial state of the matter as a solid, liquid, or gas,the molecular bond energy, and the ease with which electrons can bestripped from their orbits, among other variables. The percent of thesamples that actually become a plasma is usually very small due to thelarge energy requirements to create a plasma (i.e. ˜0.1% of a mole).Further, a plasma can be constrained by magnetic fields lowering theinput energy necessary. A sustainable plasma often requires a vacuum ormagnetic field control since the plasma elements quickly seek to begrounded, quenching the plasma; however, some systems may form shortduration plasmas on the order of nano- or micro-seconds depending uponenergy input and degree of vacuum/magnetic field present.

Some prior art references disclose electrosurgical devices with claimeduse of a gas plasma consisting of an ionized gas that is capable ofconducting electrical energy. In certain of these devices, eitherambient air or a supplied gas is used for ionization, such as thedevices disclosed in U.S. Pat. Nos. 5,669,904, 6,206,878 and 6,213,999.If a gas is supplied, it is an inert gas such as argon. In general,these devices are intended for use in ambient atmosphere for thetreatment of soft tissue.

Other electrosurgical devices function in liquid media and utilize someform of radiofrequency (RF) energy, such as with two or more electrodes.Heat is generated by use of the RF energy, resulting in destruction orablation of tissues in proximity to the electrodes. Thus the devices maybe employed for coagulation of blood vessels, tissue dissection, tissueremoval, and the like. U.S. Pat. No. 6,135,998 teaches anelectrosurgical probe immersed in liquid media or tissue, wherein anelectrical pulse is applied, with the claimed result that “plasmastreamers” are formed from the endface area of a first electrode. Inthis patent, it is claimed that cutting action results from the plasmastreamers. The minimum voltage is on the order of 1.5-2.0 kV, with 15 kVbeing the preferred maximum voltage, at a minimum power dissipation of500 Watts, and preferable a higher power dissipation of 800 to 1500Watts.

Other lower energy electrosurgical devices are known, consisting ofmonopolar and bipolar configurations that function at energyconfigurations at or below 1.4 kV and 300 Watts. Both monopolarelectrosurgical devices, in which the electrosurgical device includes anactive electrode with a return electrode separately connected to thepatient such that direct electric current flows through the patient'sbody, and bipolar electrosurgical devices, in which the electrosurgicaldevice includes both active and return electrodes, are now well known inthe art. These electrosurgical device configurations can be used inambient air or in a fluid medium. In general, it has been believed thatthese electrosurgical devices generally operate by means of creation ofa plasma or some related form of ionization. Thus prior art devices,such as that disclosed in U.S. Pat. No. 5,683,366, are claimed to relyon the fluid irrigant components participating in ionic excitation andrelaxation, with attendant release of photonic energy. This mode ofoperation is often referred to as “utilizing a plasma”. Prior artmethods claiming an ionized vapor layer or plasma include, in additionto the patents disclosed above, the methods disclosed in U.S. Pat. Nos.5,697,882, 6,149,620, 6,241,723, 6,264,652 and 6,322,549, among others.

A plasma requires that atoms be completely ionized to a gas of positiveions and electrons, and, if sustainable, would likely need to occur in avacuum-like environment. It is unlikely that many, if not most, priorart devices generate a plasma even for a short time. This most notablyfollows from consideration of the overall energy balance required toinitiate or sustain a plasma in either ambient air or aqueous, cellular,or other biologic environments. The nominal 200 to 1500 Watts of powernormally employed in a typical electrosurgical device, or any otherenergy level or configuration contemplated for electrosurgicalapplication (most, however, are between 200 and 300 Watts), isinsufficient to initiate and/or sustain a plasma, even in a vacuum andwith magnetic field control, even for a short period of time. Forexample, in a saline solution typically utilized during electrosurgery,49.6 kW-s/mole (I eV=5.13908; II eV=47.2864; III eV=71.6200; etc.) isneeded to ionize sodium, while the ionization energy of simple water is12.6206 eV (i.e. one electron volt=1.602177×10⁻¹⁹ Joules) as referencedin CRC Handbook of Chemistry and Physics, 72 ed., Lide, David R., CRCPress, 1991. The energy to initiate a plasma typically exceeds theionization potential of a material, and to sustain a plasma requires aneven greater energy input. Further, once ions have been formed insolution, such as in an aqueous solution of sodium as employed inelectrosurgery, a yet even greater energy input is required.

Further, many prior art electrosurgical references ignore recognizedphenomena relating to plasmas, such as the large ionization potentialsand energy necessary to initiate a plasma or to sustain a plasma and therole of the vacuum or magnetic fields in such circumstances. Mostelectrosurgical devices cannot deliver the energy required to initiate,let alone sustain, a plasma; and, further, electrosurgical applicationsdo not occur in a vacuum environment or in a magnetically controlledenvironment. The energy needed to create a plasma in vivo duringelectrosurgery would overwhelm the ability of the host organism towithstand such an energy insult globally. Plasma cutters as used inmetal fabrication are examples of the high energy necessary to “utilizea plasma” at normal pressures; yet such high energy levels certainlyhave not been contemplated for electrosurgical application due to thesignificant iatrogenic damage that would occur. This understanding hasled us to search for other physiochemical paradigms to understandelectrosurgery as it is practiced at energy configurations amenable andsafe for in vivo application and to more fully and correctly explaincommon physiochemical observations during electrosurgery in order tocreate more appropriate electrosurgical devices and methods.

In industrial settings, it is known to employ an oxygen and hydrogencombustion reaction, such that a “water torch” results by ignition ofco-mingled oxygen and hydrogen gas molecules liberated from waterthrough high frequency electrolysis, as is disclosed in U.S. Pat. No.4,014,777. However, such methods have never been intentionally appliedto medical procedures, such as for electrosurgical devices and methods.Further, such devices and methods have never been optimized for theconstraints of use of electrosurgical devices on biologic tissue,including constraints resulting from the presence of discrete quantitiesof electrolyte fluids, the presence of physiologic fluids and materials,the desires to minimize collateral tissue injury, the need to avoidgeneration of toxic by-products, the attendant host organism tissueresponse, and the like.

There is thus a need for electrosurgical devices that are optimized tothe true physical and chemical processes involved in the operation anduse of such electrosurgical devices upon biologic tissue within thisenergy spectrum and power range.

SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)

In one embodiment, the invention provides a method of performing anelectrosurgical procedure on a patient, the method including the stepsof providing a surgical probe including an active electrode and a returnelectrode separated by an insulator, providing an aqueous salt ionenvironment at the location wherein the electrosurgical procedure is tobe performed, the environment comprising sufficient volume to permitimmersion of at least the portion of the surgical probe including theactive electrode and return electrode, and applying current to a circuitcomprising the active electrode and return electrode, the current beingless than that required to induce plasma ionization, whereby theapplication of current induces electrolysis of a portion of the aqueoussalt ion environment thereby producing hydrogen and oxygen and furtherinitiates a hydrogen and oxygen combustion reaction. In this method, theactive electrode may include an alloy that induces release of hydrogen,including but not limited to alloys such as a magnesium alloy or a rareearth metal and nickel alloy. The aqueous salt ion environment describedin the method may include a salt ion such as an ionic form of sodiumchloride, calcium chloride, magnesium bromide, magnesium iodide,potassium iodide, potassium chloride, lithium bromide or lithiumchloride. In the practice of the method, the current applied may includea high frequency voltage difference, such as radiofrequency (RF) energy.The insulator in the method may consist of an electrical and thermalinsulator. The aqueous salt ion environment may include naturallyoccurring biological fluids of the patient, or may include an exogenousaqueous salt ion solution.

In another embodiment of the invention, a method is provided forinducing a therapeutic response in living tissue while minimizingdeleterious acid-base shifts in the living tissue, the method includingthe steps of providing a probe including an active electrode and areturn electrode separated by an insulator, the active electrode beingdisposed within an elongated lumen, providing an aqueous salt ionsolution at the site wherein the therapeutic response is desired, thesolution comprising sufficient volume to permit immersion of at leastthe portion of the probe including the active electrode disposed withinthe elongated lumen and the return electrode, positioning the activeelectrode in close proximity to the location wherein the therapeuticresponse is desired, the active electrode and return electrode beingimmersed in the aqueous salt ion solution, and applying a high frequencyvoltage between the active electrode and return electrode, the voltagebeing less than that required to induce plasma ionization. In thismethod, acid-base shifts resulting from application of the highfrequency voltage may be partially contained within the lumen. Theactive electrode and return electrode separated by an insulator may bedisposed within the elongated lumen, and optionally the position of theactive electrode along the long axis of the lumen is adjustable. By thismeans, the method may include controlling the desired therapeuticresponse by adjusting the position of the active electrode along thelong axis of the lumen. By means of the practice of the method, minimaltissue necrosis is induced at the site wherein the therapeutic responseis desired. The active electrode employed in this method may furtherinclude an alloy that induces release of hydrogen, such as a magnesiumalloy or a rare earth metal and nickel alloy. The aqueous salt ionsolution employed in this method may include a salt ion of sodiumchloride, calcium chloride, magnesium bromide, magnesium iodide,potassium iodide, potassium chloride, lithium bromide or lithiumchloride. The high frequency voltage may include radiofrequency (RF)energy. The insulator may include an electrical and thermal insulator.The therapeutic response obtained by means of the method may includenerve ablation, tissue ablation, tissue cutting, tissue coagulation,tissue modification, or induction of host healing response.

In another embodiment the invention provides a method for decreasingtissue necrosis at a site wherein high frequency voltage is applied toan active electrode immersed in an aqueous salt ion solution, the methodincluding means for minimizing the acid-base shift at the site. In thepractice of the method, the acid-base shift at the site does not causedeleterious alterations in tissue at the site. The means for minimizingthe acid-base shift at the site can include application of highfrequency voltage less than that required to induce plasma ionization.Such means for minimizing the acid-base shift at the site canalternatively include application of high frequency voltage to an activeelectrode disposed within an elongated lumen, the active electrode beingproximal the site. The active electrode may be movably disposed alongthe long axis within the elongated lumen, with the method furtherproviding for minimizing the acid-base shift at the site by adjustingthe position of the active electrode along the long axis of the lumen.

In another embodiment the invention provides an apparatus for performingsurgical procedures, the apparatus including first and second gasdelivery channels disposed within an elongated housing having a proximaland distal end, first and second gas connectors at the proximal end forconnecting the first and second gas delivery channels to a first andsecond gas source, a gas mixing plenum chamber with an inlet and anoutlet at the distal end of the elongated housing, the first and secondgas delivery channels being in fluid connection with the inlet, and anactive electrode connected to a current source, the active electrodeproximal to the gas mixing plenum chamber outlet. The apparatus canfurther include a flame arrester positioned between the gas mixingplenum chamber outlet and the active electrode. The gas mixing plenumchamber outlet may further include an acceleration throat. The activeelectrode may include an alloy that induces release of hydrogen, such asa magnesium alloy or a rare earth metal and nickel alloy. The activeelectrode may include a gas porous structure. The apparatus may furtherinclude a return electrode, including those wherein the return electrodeis in a fixed position proximal the active electrode.

In another embodiment the invention provides an electrosurgicalapparatus including a housing having proximal and distal ends, an activeelectrode disposed adjacent the distal end of the housing, the electrodecomprising an alloy that induces release of hydrogen, and an electricalconnector extending from the active electrode to the proximal end of thehousing for connecting the electrode to a source of current. In thisapparatus, the alloy may be a magnesium alloy or a rare earth metal andnickel alloy. In the apparatus, the alloy may induce release of hydrogenupon the application of current.

In another embodiment of the invention, an electrosurgical apparatus isprovided including an elongated lumen having proximal and distal ends,an active electrode adjustably positionable within and along the longaxis of the lumen, and an electrical connector extending from the activeelectrode connecting the electrode to a source of current. In thisapparatus there may further be provided a return electrode fixed inposition relative to the active electrode. The elongated lumen mayinclude an insulating material, which may be an electrically insulatingmaterial or a thermally insulating material. The active electrode may bemovably adjustable within and along the long axis of the lumen duringoperation of the apparatus, and may be adjustably positionable beyondthe distal end of the lumen. The distal end of the lumen may be in theshape or form of a segment of a cone, decreasing in diameter at thedistal end.

In yet another embodiment of the invention, an apparatus forelectrosurgery is provided including an active electrode, a returnelectrode fixed in position relative to the active electrode, and aradiofrequency power supply in electrical connection with the activeelectrode and return electrode, the power supply generating lessradiofrequency power than that required to induce plasma ionization,whereby on immersion of the active electrode and return electrode in anaqueous salt ion environment, the application of radiofrequency powerinduces electrolysis of a portion of the aqueous salt ion environment,thereby producing hydrogen and oxygen, and further initiates a hydrogenand oxygen combustion reaction.

A primary object of the present invention is to provide anelectrosurgical device that regulates the rate of combustion inunderwater environments, such as combustion in aqueous, cellular andbiologic environments.

Another object of the present invention is to provide an electrosurgicaldevice that provides tissue dissection, ablation and the like by meansof an oxy-hydro combustion reaction, wherein the oxygen and hydrogen areproduced by means of electrolysis.

Another object of the present invention is to provide a device andmethods that eliminate the need for use of an ionic solution, such assaline, to foster oxy-hydro combustion reactions at the surgical site.

Another object of the present invention is to provide for oxy-hydrocombustion that utilizes the salt ion fluid of intra-cellular structuresto sustain electrolysis and combustion.

Another object of the present invention is to provide for acid baseshifts in micro-cellular probes that utilize the salt ion fluid ofintra-cellular structures to regulate and sustain electrolysis andcombustion.

Another object of the present invention is to employ electrodes thatliberate a gas useful for combustion, such as hydrogen, upon theapplication of power to such electrode.

Another object of the present invention is to provide devices employinglower energy levels to achieve ignition of oxygen and hydrogen gasesresulting from local hydrolysis, such ignition and subsequent combustionproviding the desired tissue dissection, ablation and the like.

Another object of the present invention is to provide an electrosurgicaldevice with lower energy requirements, thereby resulting in a lower netenergy transfer to local tissue structures, whereby there are lowerlevels of collateral tissue damage.

Yet another object of the present invention is to provide anelectrosurgical device that provides combustion gases, such as oxygenand hydrogen, as part of the electrosurgical device.

A primary advantage of the present invention is the ability to optimizeionic salt solutions for the oxy-hydro combustion reaction.

Another advantage of the present invention is the utilization of anacid-base throttle effect to regulate an electrosurgical device.

Another advantage of the present invention is the use of a wide range ofdifferent and novel salt solutions, in addition to the normal salineconventionally employed in electrosurgical procedures.

Yet another advantage of the present invention is the design and use ofirrigants that that optimize electrolysis, optionally limit productionof hazardous by-products, and further optionally produce by-productswith efficacious benefits.

Other objects, advantages and novel features, and further scope ofapplicability of the present invention will be set forth in part in thedetailed description to follow, taken in conjunction with theaccompanying drawings, and in part will become apparent to those skilledin the art upon examination of the following, or may be learned bypractice of the invention. The objects and advantages of the inventionmay be realized and attained by means of the instrumentalities andcombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, illustrate one or more embodiments of the presentinvention and, together with the description, serve to explain theprinciples of the invention. The drawings are only for the purpose ofillustrating one or more preferred embodiments of the invention and arenot to be construed as limiting the invention. In the drawings:

FIG. 1 is the stoichiometric chemical equation for chemical reactionsrelated to the invention;

FIG. 1A is the equation for the acid-base “throttle” effect;

FIG. 1B is the equation for a generalized form of the oxy-hydro reactionprocess;

FIG. 1C is the equation for a generalized form of the oxy-hydro reactionprocess showing the effect of varying molar coefficients;

FIG. 2 is a view of an electrosurgical probe with a retractable sheathto create a fluid chamber that activates the acid-base throttle effectof oxy-hydro combustion in an aqueous ionic solution;

FIG. 2A is an isometric view of the retractable sheath of FIG. 2disclosing a fluid chamber that activates the acid-base throttle effectof oxy-hydro combustion in an aqueous ionic solution;

FIG. 3 is a view of an electrosurgical electrode utilizing a metal alloythat releases elemental gases upon excitation by electric current;

FIG. 4 and FIG. 4A are top and side views, respectively, of anelectrosurgical probe providing conduits for directing the flow ofelemental oxygen and hydrogen gases, a co-mingling plenum, and ignitionelectrode to ignite the oxy-hydro combustion process;

FIG. 5 is a graph depicting the acid-base throttle effect and itsrelation to salt concentration, energy imparted to the fluid, saltcrystal precipitate partial fraction, and electrical conduction;

FIG. 6 is a view of a porous electrode used to meter the flow of oxygen,hydrogen or co-mingled enriching gases;

FIG. 7 is a view of the generalized flow in a salt-ion aqueousenvironment including the physiochemistry of oxy-hydro combustion;

FIG. 8 is a view of the generalized flow in a non-salt aqueousenvironment including the physiochemistry of oxy-hydro combustion; and

FIG. 8A depicts experimental apparatus used to determine the constituentchemical components of the electrosurgical phenomenon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS BEST MODES FOR CARRYING OUT THEINVENTION

The invention disclosed herein provides, in one embodiment,electrosurgical devices that operate in conductive media, such as anionic aqueous media. The electrosurgical devices employ combustion, andpreferably oxygen and hydrogen (oxy-hydro) combustion, as a mechanismfor tissue dissection, ablation, cutting, coagulation, modification,treatment and the like. In one embodiment, oxygen and hydrogen aregenerated by electrolysis of the media, such as a saline media,endoscopy irrigant or physiologic tissue or cellular fluid, within whichit occurs. In another embodiment, at least one of the gases oxygen orhydrogen can be generated by means of an electrode that, upon electricalexcitation, releases such gas. In another embodiment, an external sourceof oxygen or hydrogen, and preferably both, may be utilized. In yetanother embodiment, this reaction can be controlled and throttled by thelocal control of constituent acid-base physiochemical participants inthe process. In the foregoing embodiments, electrical energy, such as ahigh frequency voltage difference, and preferably radiofrequency energy,can be employed to initiate oxy-hydro combustion and, in the embodimentsso requiring, induce electrolysis of the media within which it functionsor of the tissue to which it is applied to achieve the desired goals ofelectrosurgical treatment.

The equations of FIG. 1 illustrate the chemical equations that describethe overall oxy-hydro reaction, with associated acid-base shifts,resulting from hydrolysis of water and subsequent ignition of theresulting oxygen and hydrogen as disclosed herein. It is hypothesizedthat what has been traditionally thought of as the ordinary phenomenonof electrosurgery, namely “arcing”, “electron excitation”, “molecularfriction”, “vapor layer”, “plasma formation”, “plasma streamers”, or“popping”, may more properly be understood to be a result, in at leastsubstantial part, of oxy-hydro combustion occurring within biologicconstraints. The physiochemistry of the electrosurgical process ishypothesized to consist of an acid-base shift that governs the relativeavailability of the amount of water that can be consumed as part of ahydrolysis chemical reaction. The hydrolysis reaction is driven by thehigh frequency current flowing between active and return electrodes inboth the bi-polar and mono-polar modes of operation of electrosurgicalprobes. This oxy-hydro combustion theory accounts for all necessarychemical and energy constituents that are present as well as thephysical observations of light emission and heat generation during theuse of such devices. The physiochemical occurrences of electrosurgeryhave not previously been reconciled into a single accurate and cohesivetheory.

Chemical equations 10 generally govern the process herein disclosed,whereby the initial liberation of elemental oxygen and hydrogen gases 30occurs by means of electrolysis. Given that the underwaterelectrosurgical process occurs in a salt solution, either externallyapplied or that of the tissue or cell itself, such as a 0.9% by weightsaline solution, the true role of these elements should also bereconciled. The presence and true action of the salt, i.e. sodiumchloride (NaCl) for example, can be accounted for by means of equations10. The normal stoichiometry of the electrolysis reaction dictates thatif elemental gas separation is occurring, then the solute participantsmust join with the remaining solution components of water to form acomplementary acid-base pair. This pair is shown on the right-hand sideof the upper half of equations 10 as hydrochloric acid 15 and sodiumhydroxide 20 base pair. As is well known, hydrogen and oxygen gases 30can be co-mingled without spontaneous exothermic reaction. A smallamount of energy, such as RF energy 40, is required to overcome thenominally endothermic reaction and ignite the oxy-hydro combustion. Onceignited, the reaction will continue until all the reactants are consumedand reduced to the products shown on the right-hand side of the lowerhalf of equations 10.

The equations of FIG. 1A illustrate the effect of the acid-basethrottling reaction herein disclosed. The oxy-hydro combustion processdepicted is dynamic and occurs in a fixed fluid reservoir, whichnecessarily results in dynamically changing concentrations of salt ionsas a function of electrolytic conversion of water to elemental gas. Thisequation necessarily suggests that as the acid-base shift occurs in thereservoir, less and less water is available for hydrolysis. Thisphenomenon is seen in FIG. 1A where the acid-base pair is shown inincreased molar proportion to the normal stoichiometric quantity of basereactions 10. The reduction of available water for hydrolysis is evidentin the relationship 50 of oxygen and hydrogen gas to the acid-base pair.The finding is necessarily evident from the stoichiometry, namely thatinsufficient water is available given a fixed initial eight (8) moles ofwater, based on the finite reservoir of water, with increasing resultingmolar concentrations of acid and base as oxygen and hydrogen areliberated from the solution in a gaseous state, such as by bubbling outof solution. As fewer moles of oxygen and hydrogen gas are present afterhydrolysis as in FIG. 1A, the balancing portion of atoms account for thedynamic increase acid-base concentration.

The equations of FIG. 1B demonstrate a more general case of theoxy-hydro combustion reaction process in which the ionic salt isrepresented by variable 60, where X is any appropriate group I, period1-7 element of the periodic table. This generalized reaction illustrateshow hydronium and hydroxide ions can contribute to the same overallchemical reaction known as oxy-hydro combustion.

The equations of FIG. 1C demonstrate the more general case of theoxy-hydro combustion reaction process in which the ionic salt isrepresented by variables 61, consisting of α, β, γ, and 67 , wherein themolar quantities required for stoichiometric combustion are any valuethat appropriately satisfies the oxidation reduction valencerequirements for the overall reaction. This generalized reaction caseshows how oxygen and hydrogen requirements can vary and still result inthe same overall chemical reaction known as oxy-hydro combustion.

The modes of oxy-hydro combustion operation described in FIG. 1, FIG. 1Aand FIG. 1B depict theoretical stoichiometric reaction processes inducedby application of high frequency electromagnetic energy to a salt ionsolution, including salt ion solutions typically found within biologictissues themselves. The fundamental process is governed by the rate ofelectrolysis in the initial dissociation of water into oxygen andhydrogen gas, as shown in equations 10.

Without wishing to be bound by theory, it is believed that the mechanismof action explaining operation of prior art electrosurgical devices iserroneous, and that an understanding and appreciation of the hereinhypothesized correct mechanism of action results in devices and methodsas further disclosed herein.

In prior art, it has been assumed that conventional bipolarelectrosurgical devices utilize excitation and relaxation of salt ionsresulting in photonic energy release such as through a plasma formation.The basis for such claims is that sufficient energy is imparted to thevaporized salt solution to provide electron shell excitation of thenative sodium ions. Upon relaxation of the excited electron, a photon isemitted (a foundational concept of quantum theory as originallydeveloped by Niels Bohr in 1913). However, the ionization energy permole of Na is 496 kJ as referenced in the CRC Handbook of Chemistry andPhysics, 72 ed., Lide, David R., CRC Press, 1991, pp. 210-211. Thisenergy is the equivalent to 496,000 Watt-seconds/mole. Even if onlyone-tenth of a mole of Na is present, a net energy of 49.6 kW-s/mole isneeded to ionize the sodium to form a plasma. This energy is far greaterthan the 200 to 1500 Watts of power provided by prior art conventionalelectrosurgical power supplies, methods, and devices.

Further, monopolar electrosurgical devices have been described as usinga “molecular friction” phenomenon to generate an “arc.” The implicitassumption of this paradigm is that the majority of the energy impartedby the wave/particle function of nominal waves created by theelectrosurgical power supply and device is absorbed at the naturalfrequency of the salt ions. A process called “ionic agitation” toproduce molecular friction, resulting from ions attempting to “follow”the changes in direction of alternating current, is used as one commondescription of the observed phenomenon as referenced in M. J. Medvecky,et al., Thermal Capsular Shrinkage Basic Science and Applications,Arthroscopy: The Journal of Arthroscopic and Related Surgery, 2001;17:624-635. However, ordinary microwave technology demonstrates thathigher frequencies are needed to excite water, including salt water, aswell as the ions normally contained within biologic tissue.Additionally, understanding how ions from a salt exist in solution makesit unlikely that the claimed excitations result in the observedphenomenon. A normal saline solution consists of sodium chloride (NaCl)salt dissolved in water, conventionally ˜0.9% NaCl by weight for normalsaline. Classical solute-solvent theory states that the salt (solute)will dissociate in water (solvent) to form NaOH and HCl in equilibrium.Thus the actual energy is not absorbed by a “salt” ion at all, butrather by the acid-base equilibrium ions in coexistence within thesolution media.

From these examples, it is hypothesized, again without wishing to bebound by theory, that many of processes heretofore described asresulting from a “plasma” actually are a result, at least in part, ofoxy-hydro combustion. The oxygen and hydrogen are created byelectrolysis, with concurrent ignition, all as a result of highfrequency, high voltage energy sources. The invention disclosed hereincorrectly explains the phenomenon heretofore described duringelectrosurgery observations as “arcing”, “electron excitation”,“molecular friction”, “vapor layer”, “plasma formation”, “plasmastreamers”, or “popping”. The understanding and appreciation of thisdisclosed mechanism of action enables further electrosurgical device andmethod embodiments that more accurately follow in vivo physiochemicalprocesses and open such embodiments to new applications not previouslyenvisioned for electrosurgical devices and methods as disclosedheretofore.

In one such embodiment, the devices and method of this invention includea means to deliver one or more gases required for combustion to asurgical site, without the need to perform electrolysis to liberatehydrogen and/or oxygen for the combustion process. In one preferredembodiment, both oxygen and hydrogen gases are provided for thecombustion process, with ignition through electrode means. The gases maybe in a compressed form, and optionally are metered via throttlingvalves and mixing chambers. The gases, such as oxygen and hydrogen,delivered via a suitable conduit to an electrosurgical device. The gasesare delivered to the distal end of said device where they are ignitedusing a voltage source and an ignition device. The resulting combustionzone is sufficiently controllable to enable treatment of smallbiological structures and sufficiently scalable to permit treatment ofcomparatively large areas.

In another such embodiment, the devices and methods of this inventioninclude an electrode that liberates an elemental gas, such as hydrogen,without electrolysis. Thus metal alloys and compositions whereinelemental gases are liberated upon providing power to such electrode areprovided. Such metals and alloys thereof are disclosed in U.S. Pat. Nos.5,964,968, 5,840,166, 5,746,896 and 5,494,538, incorporated herein byreference. Such compositions may be made into electrodes or similarstructures that liberate elemental gas, such as hydrogen, when subjectedto an electric current. Use of these metals in the active electrodeprovides an enriched combustible gas environment, thereby fostering morerapid and intense oxy-hydro combustion. In addition, the use of suchmaterials reduces reliance on electrolysis to produce combustion gasesor the need for a conduit to deliver combustion gases to the combustionsite.

In yet another such embodiment, the devices and methods of thisinvention provide shielding to the electrosurgical device, andpreferably a bipolar electrosurgical device including at least twoelectrode elements, whereby the shielding is employed to advantageouslyutilize the acid-base throttle effect of oxy-hydro precursor reactions.The shielding, which may be a telescopic sheath, may be employed tocreate a fluid reservoir that both limits oxy-hydro combustion via theacid-base throttle effect and further advantageously distances theactive electrode from the surgical site.

Additional benefits are gained from understanding the physiochemicalprocess involved in this phenomenon as disclosed. Further, increasedknowledge is gained regarding mechanisms of patient injury observedduring the application of prior art electrosurgical devices and methodsthat shed further light upon these processes. For example, it is knownthat in the prior art paradigm of electrosurgery, the electrical currentflows through the path of least resistance. It is also documented in theliterature that the typical nerve function disruption resulting frommonopolar electrosurgery has been thought to result from heat effects ofthe probe through concepts described as “depth of necrosis” or “thedepth of penetration of the heat”, even though temperature studies havenot fully borne such a conclusion. This apparent inconsistency can nowbe understood in that the path of damage that occurs is not one ofcollateral heat induced damage, but one of the physiochemical oxy-hydrocombustion acid-base shift reaction disclosed herein. The alteration ofthe acid-base milieu that normally results from electrosurgery isclinically observable in the nervous system, since the nervous system'sclinical function is most sensitive to acid-base shifts. The alterationin nerve conductivity induced by the acid-base shift is resultant fromdirect changes in membrane ionic function and electrical pulsepropagation for nerve conduction. The normal tissue response to such anacid-base insult is to metabolically correct the disruption and resumenormal function. If the effect was due to thermal damage, the healingresponse would be quite different and follow a different time coursetypical of that type of insult. Clinically, a quick resolution offunction typical of metabolic alterations (short effective refractoryperiod of membrane responsiveness) is observed, rather than that ofthermal damage (prolonged effective refractory period of membraneresponsiveness). Acid-base buffering systems of the body fluids providethe most immediate defense against changes in acid-base environment andprovide an important response to treatment. Phosphate and bicarbonatebuffers are examples of these systems that function locally. Eachacid-base or metabolic/structural disturbance is followed by thetissue's response to such a disturbance, and this response can be usedfor therapeutic protocols. The complete effect of electrosurgicaloxy-hydro combustion acid-base shift tissue treatment within the bodygoes beyond heat alone, and includes more profound metabolic alterationsinduced by the acid-base shift phenomenon as well as the host organismresponses induced by the device and method of application.

The physiochemical processes disclosed herein further reconcile the useof a typical electrosurgical probe in the ambient air, underwater,cellular, and/or biologic environment to produce sufficient heat andother metabolic effects for the efficacious application of energy tobiologic tissue structures as part of the ablative, coagulation,modification, or other surgical processes. The general functions ofthese probe embodiments are those of a tissue modifier, such as bycoagulation or cutting, that induce a healing or reparative hostresponse. In the coagulative lower relative energy function, forexample, the dominant physiochemical reaction is initial electrolysisreaction 10. In this mode of operation, a typical electrosurgical probeproduce localized acid-base pair equilibrium at an elevated temperaturedue to the heating effects of the active electrode resistive heattransfer to the solution. Metabolic affects are important in vivo withsuch application. As the amount of energy delivered to the activeelectrode is increased, the energy delivered to the oxy-hydrogenco-mingling gases becomes sufficient to ignite the oxy-hydro combustionreaction and sustain electrolysis simultaneously with both reactions 10(FIG. 1) active in this overall process. This process describes acutting function of electrosurgical devices. However, in no instance hasa plasma been formed.

This graded effect as described by FIG. 1 also explains otherelectrosurgical observations. For example, there exists a transitionalpower input where the energy delivered to the active electrode cannotsustain a sufficient electrolysis rate to support continuous oxy-hydrocombustion. This results in what is frequently observed as a “popping”operation of an electrosurgical probe. In this mode of operation thecombustion process consumes the available co-mingling gas volume throughthe combustion reaction, thereby producing water, resulting in collapseof the gas volume and quenching the thermal energy delivered by theactive electrode. As a result the active electrode is cooled and for atransient period there is insufficient gas volume or heat to sustain anoxy-hydro combustion. Electrolysis necessarily must then reestablish thegas volume necessary to sustain the oxy-hydro combustion reaction. Asenergy input to the electrode is increased the rate of electrolysisbecomes sufficient to prevent the collapse of the oxy-hydrogen gasvolume as the combustion reaction takes place, and continuous oxy-hydrocombustion is sustainable. In another such embodiment of the invention,exploitation of the acid-base throttle can be used to control thedirection and magnitude of the physiochemical processes disclosed hereinto avoid the uneven physiochemical flow evidenced by “popping”.

Based upon the understanding of the hypothesized electrosurgical processset forth herein, the variations of possible processes become evident.FIGS. 1B and 1C illustrate general potential modes of operation that anelectrosurgical process can embody. In this case the reaction isdescribed by the coexistence of hydroxide and hydronium ions, whichparticipate in the oxy-hydro combustion reaction process. The sameprinciples that govern the salt-ion reaction process apply to thegeneralized case and further reveal what forms in which the overallreaction can manifest itself.

It may thus be seen that the methods and devices of this invention maybe employed for electrosurgery on any living biologic tissue that iscomposed primarily of water, salts such as sodium chloride, and mineralsin solution. The tissue changes that can be induced include tissueablation, vaporization, coagulation, cutting, modification, andinduction of host responses that are deemed therapeutic. In general, itis possible and contemplated to induce non-necrotic tissue modificationsconducive to normal healing or reactive responses as an importantmanifestation of this disclosed electrosurgical application.

As an example, it has also been discovered and is contemplated that themethods and devices of this invention may be employed for fusing orwelding bone-related tissues, such as is disclosed in pending U.S.patent application Ser. No. 09/885,749, entitled Method For Fusing BoneDuring Endoscopy Procedures, filed Jun. 19, 2001, and incorporatedherein in its entirety. In brief, if bone fusion or welding is necessaryas part of a surgical procedure, a piece of autologous bone can beharvested from another part of the body, or alternatively an allograft,synthetic composite, combination composite of synthetic and biologicorigin, genetically engineered bone material or other materialscontaining bone-derived collagen material or a mimetic thereof,including a composite including type I collagen, is utilized. Theportion of harvested bone or alternative substitute is prepared, such asby ex vivo chemical or mechanical treatment to remove or alter themineral matrix and provide a good fusion or welding surface. Similarly,the in vivo bone contacting surfaces may optionally be treated to removeor alter the mineral matrix, and a biocompatible “de-fat” procedure isemployed. The harvested bone or alternative substitute may further bemodified to include an interfacing agent for the fusion or weldingprocess.

The harvested bone or alternative substitute and/or the recipient bonemay be chemically or mechanically treated to remove or alter the mineralmatrix and provide a good fusion/welding surface. Because thefusing/welding occurs in a fluid medium and in vivo, any chemicalutilized upon the recipient bone in particular must be safe to the humanor animal and to the tissues being treated. In the case of acidpre-treatment of bone surfaces, dilution is necessary. Or, other acidsor chemical compositions, friendly to the host, may be used such asacetic acid, citric acid, malic acid, or other acids found normally inhuman ingested foods or endogenously produced by the host organism.Generally, the harvested bone tissue is treated with demineralizationprocedures and the recipient bone is treated with biocompatible agentsto “de-fat” the porous intersticies, such as hydrogen peroxide,evacuating those spaces to accommodate the introduction of a bioactiveinterfacing agent. The bioactive interfacing agent may include abiocompatible acid-treated bone-derived graft material, a carriersubstance that allows use in a fluid environment, a visualization aid, asubstance that channels the electromagnetic energy, and anosteinductive/osteoconductive compound or compounds. An example of sucha composite would be citric acid, bone graft, hydroxyapetite, andtricalcium phosphate gel. Such configuration provides greater stabilityof manipulation and of placement in an in vivo fluid medium such asduring endoscopy. The surfaces of the bones to be fused or welded arecontacted, preferably with the interface agent positioned therebetween.Fusion or welding is by means of the devices and methods disclosedherein, preferably employing a source of radio frequency electromagneticradiation. To those skilled in the art, it is clear that the acid-baseinvolvement of the process disclosed herein is directly related to therelative demineralization harnessed for the bone welding process.

Thus methods and devices of the invention described herein may beemployed with any of a wide variety of tissues, including withoutlimitation any soft tissue or hard tissue, or soft tissue-derived andbone-derived products and/or materials. In the case of collagen tissues,the methods and devices can further be employed to fuse, weld orotherwise join such tissues such as for bone welding, vascularanastomosis, neurorraphy, and the like. Further, as acid-base shiftsaffect cell membrane permeability, such changes can be harnessed fortherapeutic measures, as described hereafter.

It may further be seen that certain embodiments of the inventiondescribed herein may be employed in applications where prior artconventional monopolar devices are employed, such as in a non-conductiveaqueous media of some endoscopy fluids. Even where themacro-environment, such as endoscopy fluids, is non-conductive, themicro-environment, in proximity to the electrodes and devices hereafterdescribed and the biological tissues to be modified, is necessarilyconductive. Thus the methods and devices described herein may, with suchmodifications as are required and will be apparent to one of skill inthe art, be employed in applications where prior art conventionalmonopolar devices are now employed. Similarly, the methods and devicesdescribed herein may be employed in applications where prior artconventional bipolar devices are employed, such as environments whereina conventional conductive aqueous media is employed. Further, themethods and devices described herein may be employed in applications oftraditional open surgical procedures, i.e. in ambient air (versusendoscopic procedures), with the host biologic tissue itself serving asthe fluid reservoir or fluid environment.

The devices and methods of this invention have been employed with avariety of solutions, including 0.9% NaCl, 0.9% KCl, H₂SO₄, HCl,distilled H₂O, and a glycine solution, and a variety of stateparameters, including varied pH and temperature. Further, the devicesand methods of this invention have been employed without solutions inthe macro sense, and been use in “ambient” air conditions of hydratedand normal biologic tissue. In addition, a variety of RF energy settingshave been employed, such as the embodiment of 150-2000 Volts peak topeak with a range of power settings between 5 and 500 Watts. Based onanalysis of various solutions, states, and energy profile applications,the general equation of FIG. 1C was validated, and data obtained for thegraph of FIG. 5. Although the energy input required to initiate and/orsustain a plasma markedly exceeds these levels (or any levelscontemplated for electrosurgical application), even for the mostfavorable plasma generating conditions (refer to above ionizationdiscussion for typically encountered constituents of a biologic systemduring electrosurgery), the transition from electrolysis and combustionto that of plasma formation based upon energy input has not beendetermined. It is anticipated that as energy level is increased,significantly surpassing the ionization potentials of the constituentsof a biologic system, electrolysis and combustion would yield to plasmaformation; however, this transition point far exceeds the levels ofenergy that an organism can withstand and is not contemplated forelectrosurgery due to the significant iatrogenic injury that would beinduced. The energy configurations typically employed in andcontemplated for electrosurgery, and those that we have verified asdiscussed above, provide sufficient energy to initiate and sustain theelectrolysis and combustion reactions 10 as disclosed herein, allowingfor the use of such physiochemical reactions for therapeutic means asfurther disclosed herein.

Further, microscopic examination of various human tissue types,including ligament, articular cartilage, and fibrocartilage, wasconducted both prior to and subsequent to application of RF energy atlow power settings of between 5 and 40 Watts for short time durations,on the order of two to five seconds. The observed histological changesappear visually identical to those induced by changes in the acid-basestate. Altered cell membrane structure and permeability, cellularosmotic states (dehydration, swelling, etc), and changes in thestructural properties of intracellular organelles were evidenthistologically. The histological changes did not result in cellulardestruction, and were compatible with inducing a healing response in theaffected tissue. Normal tissue response is to metabolically correctdisruptions and resume normal function. Further, it was observed that byuse of a prototype probe incorporating both an active and returnelectrode, it was possible to induce similar changes without actuallytouching the tissue, thus resulting in a desired alteration withoutdirect contact of the probe to the tissue. In one embodiment, a smallfunnel or cone tip on the probe permitted resulting energy to bedirected toward the tissue, thereby resulting in a very small andisolated area of delivery of energy.

Use of the methods and devices of this invention permit micro-scaletreatment of living tissue, without necrosis, and induce or permit anormal healing response of that tissue. It is hypothesized that bycontrolling the energy and reaction as generally described by theequations of FIGS. 1A to C, it is possible to provide sufficient heatenergy to cells to induce natural repair mechanisms without inducingpermanent injury to the cells, while maintaining an acid-base shift inthe immediate cellular environment that is not unduly deleterious, andmay in fact advantageously result in changes to cellular membranepermeability desired for treatment therapeutics (a derivative of theclinical nerve example above and the histological data disclosed above).Such alteration in permeability may allow introduction of othertherapeutic agents which otherwise would not have been efficacious.Further, the heat application can induce gene expression of the heatshock or other class proteins typical of that induced systemically byfever. This heat induction controlling gene expression can now beinduced locally by the use of the methods and devices disclosed herein.

In general, it is believed that the relationships between salt content,temperature, dissociation properties in solution, pressure, pH, energyand the like follow non-linear mathematical relationships. As discussedhereafter, application in a surgical environment necessarily is in afinite and definable reservoir. Differential equation sets may bedeveloped to model the mechanisms described in this invention in afinite reservoir, such as for example a knee joint. Additionally, thefluid mechanics of the arthroscopic devices and methods employed in asurgical procedure may be modeled by analysis of issues such as fluidflow rate, delivery method, pressure, currents, and reservoir anatomy,such as anatomy of a joint on which a surgical procedure is performed.By varying determining and analyzing such parameters, other and furtherembodiments of the invention herein present will become apparent tothose skilled in the art.

The process, methods, and devices disclosed herein are furtherelucidated via a series of experiments and additional embodiments.

FIG. 8A depicts a device for collecting and sampling the oxy-hydrogengas combustion reaction by-products. In experiments utilizing theapparatus shown in FIG. 8A reaction products of the electrosurgicalphenomenon were collected and analyzed to determine their makeup. Gasspecies were analyzed to determine both make-up and relativeconcentrations. An apparatus for collecting the gaseous emissions from astandard bi-polar electrosurgical probe was assembled and used in asaline bath. Gas collection tube 450, was inverted and filled with 0.9%by weight saline, as was Pyrex glass solution bath container 480. Thefilled gas collection cylinder was then carefully stoppered and replacedin the bath to form a manometer water column that could be displaced bycollected gas. Typical bi-polar electrosurgical probe 420 was bent toaccommodate the gas collection tube inlet and fixed for the duration ofthe experiment. Gas collection tube 450 was attached to flexible tubingand then to evacuated summa canister 510 for gas sample collection.Electrosurgical console 410 was set to a maximum power output of 180 Wfor probe 420. Gaseous emanations were observed at the electrode tipduring the “firing” of the probe. Bubbles 200 naturally floated up intocapture section 460 of tube 450 because of buoyancy forces and wereallowed to accumulate and displace approximately 95% of the total volumeof the tube. When the tube was filled to maximum capacity the firing ofthe probe was stopped and the gas carefully evacuated from the top oftube 450 via means of partially opening stop-cock valve 440 to form arestriction, and sequentially opening needle valve 500. The combinedflow restrictions created by valves 440, 500 and flow restrictor/filter470 made metering of the inlet of the gas rate manageable to avoidunwanted water uptake by summa canister 510. The process of firing theprobe, capturing the gaseous emanations, evacuating off the filled tubeand filling the summa canister was repeated six times to captureapproximately a total of 180 ml of gas in the summa canister. Thecanister was left with partial vacuum intact by using pressure gauge 490to determine the final negative pressure. This pressure was checked bythe receiving laboratory to ensure that inadvertent uptake ofcontaminating atmosphere has not happened during transport of thecanister to the examining laboratory. The gas was subsequently analyzedfor N₂, H₂, CO, CO₂, CH₄, C₂H₆, and C₂H₄. laboratory analysis showed anear perfect ratio of 1.933:1, hydrogen to oxygen, in agreement with theequations of FIG. 1. In a second experiment the presence of acid-basepairs in the solution remaining after combustion was examined. This wasaccomplished by using pH meter 530 in conjunction with dielectric pHprobe 520 to take a baseline measurement of salt solution 430, withperiodic measurements as the experiment progressed. Solution bath 480represents a finite reservoir of solution and thus the increasingmolarity of salt-ion solute should have the effect of increasing acidityof the bath 480. In fact, experimental data show a nominal shift ofapproximately 2 pH acid, which confirms the presence of acid-base pairsas predicted by the stoichiometry.

Chemical analysis yielded findings that support the stoichiometry shownin FIGS. 1A and 1B. Hydrogen and oxygen gases were found to be presentin exactly a 2:1 ratio as shown in 30.

FIG. 2 is a view of a preferred embodiment of an acid-base throttlesheath probe used in the underwater, cellular and biologicelectrosurgical environment. Translating sheath 80 is employed to createan acid-base trapping zone and thereby harness the acid-base“throttling” effect of lowering the available moles of electrolyzedoxy-hydrogen gas, thereby reducing the net heat of reaction in theoxy-hydro combustion. Translating sheath 80 extends itself beyond themost distal portion of active electrode 70 to form a plenum chamberwherein acid-base pairs are allowed to collect and decrease thereactants of oxy-hydro combustion. Current flows between activeelectrode 70 and return electrode 140 to complete the electricalcircuit. Sheath 80 can be selectively positioned by using slidingratcheting finger switch 120 via coupler guide stanchion 110 andpush-rod 100 to set the desired quantity of acid-base entrapment andtune the rate of reaction observed at active electrode 70. Activeelectrode lead wire 75 is constructed to have sufficient slack withinthe probe body that translation of active electrode 70 is notconstrained by connected lead wire 75. Sheath return spring 90 istensioned by translation of push rod 100 as sheath 80 is extended to itsmost distal position, and is retained by finger switch ratchetingmechanism 120. When released, sheath 80 is pulled by return spring 90into its normally proximal position.

FIG. 2A illustrates another view of a preferred embodiment of theacid-base throttling sheath. In this view acid-base throttle sheathmechanism 80 is in the distally extended position. Freedom of travel isshown by translation direction arrows 170. The electrical circuit iscompleted between active electrode 70 and return electrode 140. Both theactive and return electrodes are conductively isolated from each otherusing thermal and electrical insulator 150 which may preferably beconstructed of a ceramic or high temperature polymer. The remaining areaof the return electrode is insulated by insulating sheath 180. Asdepicted, the energy applied to the probe is only sufficient to generateelectrolysis and is fully consumed by said reaction. Insufficient excessenergy exists to ignite the co-mingling oxy-hydrogen gases and thus onlythe products of the first of reactions 10 are created. During typicalapplication of low-level RF energy acid-base pair density streak lines160 are plainly visible to the naked eye; these are byproducts of theelectrolysis reactions known to govern the overall process.

The translating sheath 80 may be cylindrical, as depicted, or may beconical, or may alternatively have a conical or cone tip. In this way,the size of the probe may be reduced, and the shape or configuration ofthe electrodes and sheath may be such as to direct energy in a desiredpattern or manner, so as to provide maximal energy delivery to adiscrete area to be treated, while minimizing injury to adjacenttissues. Similarly, in this way energy may be directed to the area to betreated without the probes or electrodes actually contacting such area.

In the operation of the preferred embodiment of FIGS. 2 and 2A theoxy-hydro combustion process is mechanically adjusted to suit thedesired intensity of operation. Active electrode 70 generates theoxy-hydro combustion reaction, while translating sheath 80 can bepositioned to create a convection trap for acid-base pairs 160 generatedas part of the oxy-hydro combustion reaction process. Increasing theconcentration of the acid-base pairs reduces the net available oxygenand hydrogen gases that can be generated by the electrolysis reaction.This, in turn, leads to a decreased intensity of the overall reaction.This effect is defined herein as the acid-base throttling effect on theoxy-hydro combustion reaction process. The translation of sheath 80alters the conducted electrical pathway of the RF energy. The sheath,when constructed of a non-metallic substance, does not alter thetransmission pathway. By positioning the sheath using ratcheting fingerslide 120, coupler guide stanchion 110 and push-rod 100 in combinationthe oxy-hydro combustion reaction can be trimmed to the most desirablelevel of intensity. Additionally, in surgical modes of operation whereno tissue contact is desired the throttling sheath can be used to fixthe distance to the tissue and provide a consistent tissue treatmentbenchmark distance. When combined with manipulation of delivered powerto the active electrode, a precise control of both the oxy-hydrocombustion reaction and the surgical process can thus be achieved.

FIG. 3 is a preferred embodiment wherein the active electrodecontributes elemental gases to the oxy-hydro combustion reaction. Thisembodiment illustrates the case where sufficient excess RF energy isimparted to the electrolyzed gas to ignite the mixture, reduce thereactants, and release heat and light. In this case, active electrode 70is manufactured from an elemental gas-storing metal alloy, such as thosedisclosed in U.S. Pat. No. 5,964,968, that is used to enrich theelectrolyzed gas process and facilitate an increased rate of reaction.Active electrode 70 releases elemental gas 220 such as hydrogen oroxygen, optionally upon electrical excitation by RF energy. This energyis used to complete the electrical circuit between active electrode 70and return electrode 140, separated by insulator 150, via current flow190. Oxy-hydro combustion zone 210 is thereby enriched with excessgaseous reactant and can more readily accommodate combustion even in therapidly fluctuating, semi-quenched, fully-immersed environment. Normalheating effects due to the conducted portion of the absorbed energy fromcurrent flow 190 cause immediate density changes in addition to anacid-base shift that allow for the oxygen and hydrogen gases to escapecombustion zone 210 without being ignited. The buoyancy created by thedensity change has a resultant velocity vector 230 that governs the rateof gas escape, and in normal electrosurgery the entire field of surgeryis normally kept under constant flow with velocity vector 240.

Active electrode 70 can release any desired elemental gas, but in apreferred embodiment the elemental gas released is hydrogen. Oneexemplary alloy that may be employed is a magnesium alloy capable ofinducing generation of hydrogen when reacted with water in the presenceof a salt containing chlorine, the alloy containing between 0.4% and 10%by weight nickel and between 0.015% and 10 by weight zinc, as disclosedin U.S. Pat. No. 5,494,538. Another exemplary alloy that may be employedis a rare earth metal-nickel hydrogen storage alloy, including thealloys disclosed in U.S. Pat. Nos. 5,840,166 and 5,964,968. In general,hydrogen releasing rare earth alloys of the AB₅ type are known,containing light rare earth elements such as La, Ce, Pr, Nd or mixturesthereof in the A site, and Ni, Co, Mn, Al or mixtures thereof in the Bsite. These alloys permit hydrogen adsorption and desorption, optionallyin response to application of energy, such as RF energy.

In the operation of the embodiment of FIG. 3, the electrode thussupplements gas production, and preferably hydrogen production. Theactive electrode is comprised of a material that enriches and/orenhances the overall oxy-hydro combustion reaction. Under ordinaryunderwater, cellular, and biologic electrosurgical conditions whenelectrolysis takes place natural buoyancy 230 of the generated gas isaugmented by heating effects of active electrode 70 and therebyincreases net buoyancy forces acting on the gas. This conditiongenerally contributes to an accelerating of the gas away from the activeelectrode. To further exacerbate the problem the normal mode ofoperation of underwater, cellular, and biologic electrosurgery isusually done in a flowing environment, which imparts a flow velocityvector 240 to the overall fluid field. To counteract the amount of“lost” gas from both bubbling off and flow, a means is provided wherebyimmediate oxy-hydro combustion zone 210 can be enhanced with elementsthat contribute to the oxy-hydro combustion reaction process. As RFcurrent energizes active electrode 70 a release of elemental gas 220takes place directly into the co-mingled oxygen and hydrogen gascombustion zone. This augmentation of the ongoing electrolysis reactioncan be used as a quenching element by providing excess gas, therebyreducing the net combustion heat output. Alternatively, the augmentationby liberated gas 220 can be used to optimize stoichiometry, therebyoptimizing and maximizing oxy-hydro combustion heat output.

The amount of liberated elemental gases, such as hydrogen, may bedetermined and adjusted as appropriate for a specific treatment purpose.For microprobes employed in cellular applications, even very smallamounts of additional hydrogen provide fuel theoretically adequate for acellular response.

FIG. 4 and FIG. 4A depict a preferred embodiment wherein independent gasflow lumens are provided for the delivery of elemental gases to theprobe tip. In this embodiment an electrosurgical oxy-hydro probeprovides means for independent delivery of elemental oxygen and hydrogengas to the probe distal tip reaction zone. Elemental gases arepressure-driven through gas transmission lumen sections 275 separated bygas conduit wall section 270 to prevent premature co-mingling of theelemental gases. Upon exit from the lumen sections the gases are mixedin plenum chamber 260 to facilitate combustion reaction process. Thegases are then accelerated through converging nozzle section 250 toenhance dynamic pressure, thereby driving the oxy-hydrogen gas throughflame arrester 280. The gas is then channeled upward through insulator150 toward active electrode 70 to initiate the oxy-hydro combustionreaction process. In this specific embodiment the need for anelectrically conducting irrigant is completely eliminated. FIG. 4Aillustrates the separation of the electrical circuit power deliveryconduction portion of the probe in isolated electrical channel lumen141. Active electrode lead wiring traverses the lumen length to thedistal portion wherein it is electrically connected to active electrode70 and can complete a transmission circuit via electromagnetictransmission field lines 195 across insulator portion 150 to returnelectrode 140. Oxy-hydro combustion zone 300 is created by the ignitionof the co-mingled gases being forced from the electrosurgical probedistal tip under fluid pressure. The rate of reaction can be governed bymetering of the flow rate of the individual elemental gases or by“starvation” of either elemental gas to run the reactionsub-stoichiometrically “lean” or “rich”, which will alter the net heatof reaction according to normal principles of combustion reactionchemistry.

The operation of this embodiment illustrates how the need for a liquidirrigant medium can be completely eliminated. Pressurized elementaloxygen gas and hydrogen gas are independently delivered to probe tipinsulator 150 via isolated lumen section 275 and after mixing areignited by heat generated at active electrode 70 from solid/fluidinterface transmission wave generation heating. The intensely hot flamegenerated can be used for a variety of purposes in a surgical setting.Additional advantages in this specific mode of operation become evident.The power needed to ignite the co-mingling oxy-hydrogen gas mixture isreduced because the conducted portion of the energy needed toelectrolyze is now no longer necessary. Only that portion of the energythat provides heating to the active electrode sufficient to ignite themixture is necessary to sustain the combustion. FIG. 4A illustrates usesin conjunction with a fluid irrigant that provides further enhancingcapability to the oxy-hydro combustion reaction process. In many caseshaving intense heat sources within the human body is undesirable, anduse of an irrigant can provide multi-faceted additional advantages, themost apparent of which is as a quenching media to reduce collateral heattransfer to healthy tissue structures. Such an irrigant is preferablycomposed of acid buffering agents that form a solution resistant tochange in pH when either acid or base is added, such as from the naturalprocess of oxy-hydro combustion.

FIG. 5 depicts the general energy absorption curve for the electrolysisand ignition of the oxy-hydro combustion reaction process. The curvesdepicted show the multi-dimensional aspects of the immersed environmentand how they affect the overall combustion process. It is important tounderstand that the net energy consumption of the entire processconsists of two distinct components of RF energy, conduction andtransmission. Conducted energy 320 is consumed in the molecular electrontransfer between ions in solution. Transmitted energy 310 involves theelectromagnetic wave function that is typically involved with radio-wavetransmission. Both elements are present in ambient air, underwater,cellular, and biologic electrosurgery and contribute separate anddiscrete energy functions to the overall process. As shown in FIG. 5 themode of energy consumed is dependent on the relative concentration ofsalt ion in solution. As the salt ion concentration approaches zero thebulk of the energy is consumed through conduction as pure water is onlymoderately conductive. Some transmission 310 actually occurs at allstates and is therefore shown as a smaller portion of the overall energyconsumed. As salt ion concentration increases the solution resistivitydrops and the amount of energy consumed through conduction 320 alsodrops. Sufficient resistivity of the solution media remains that heatingtakes place as part of the conduction process, but the active electrodebeing heated by its own metallic resistance at the liquid-metalinterface delivers the majority of the heat generated prior to ignitionof oxy-hydro combustion reaction. As the salt ion concentrationcontinues to increase, conduction resistivity continues to drop until arelative minimum of conduction resistivity 340 is achieved. At thispoint in oxy-hydro combustion energy absorption process curve 330 themajority of the energy consumed is through transmission 310. In allcases the curve defines the total energy input for which oxy-hydrocombustion ignition can be achieved. However, at the optimum salt ionconcentration point 340 the minimum amount of input energy is requiredto both electrolyze the solution and ignite the oxy-hydro combustionreaction.

If the salt ion concentration is increased further still, while holdingthe solution temperature constant, a partial fraction of solid salt ionwill co-exist as a suspension, the overall solution having reachedsaturation limit 370 for the given temperature. Curve portion 360illustrates the energy absorption required for oxy-hydro combustionignition as the partial fraction of salt ion is increased beyondsaturation limit 370 for the solution. As the salt ion concentration isincreased beyond saturation limit 370 along curve 360, both conductionand transmission resistivity are generally increased and the net energyrequired to achieve oxy-hydro combustion ignition is also increased.Curve 350 illustrated the shift in solubility created by increasingsolution temperature. Temperature rise in solvent is known to increasesolute capacity; this condition is commonly referred to as“super-saturation.” As the solution is heated, whether artificially orpurely by conducted heating from the active electrode, the energyrequired for oxy-hydro combustion is increased. From equations 10, itcan be seen that this is a result of greater concentration of salt ionfraction in the equilibrium state of acid-base pairs, which reduce thenet amount of water that can be electrolyzed into oxygen and hydrogengases. This specific condition is an artifact of a finite reservoir. Inmany surgical situations, as the fluid is in constant flow there is noexcessive buildup of acid-base pairs, since they are “flushed” away inthe flowing solution.

It can be appreciated from the chart in FIG. 5 that the acid-basethrottle effect can be overcome through the addition of RF energy as theconcentration of acid-base in solution rises. This is most advantageousin understanding why maintaining an optimum flow throughout the surgicalfield proves beneficial in electrosurgery. Too much flow and the heatedbuoyant gas escapes more rapidly than it can be combusted and becomesuseless to the surgical process. On the other extreme too little or noflow leads to excessive heating and build-up of acid-base that can havedeleterious tissue effects if left to accumulate for an extended period,including tissue and nerve damage or necrosis. The graph reveals thatthe solution temperature will have an indirect performance effect inallowing probe operations that vary widely from the optimum energyminima of concentration point 340.

FIG. 6 is a view of an embodiment wherein the active electrode includesa porous gas-liberating alloy. Elemental gas is delivered under positivepressure to active electrode 390 and forced through pores in theconductor. The enriching gas stream exits in diffuse gas stream 380 andenters the oxy-hydro combustion zone. Electromagnetic energy issufficiently imparted to the combustion zone to liberate elemental gasfrom the electrode alloy and ignite the enriched co-mingled mixture. Theelectromagnetic energy is delivered in transmission from activeelectrode 390 to return electrode 140, which is both thermally andelectrically insulated by insulator 150. Insulator 150 can preferably bemade from high temperature refractory ceramics or ceramic alloys.Elemental diffuse gas stream 380 is comprised of molecular hydrogen gas,molecular oxygen gas, or co-mingled oxygen and hydrogen gases to enrichthe oxy-hydro combustion zone.

In mode of operation of the device of FIG. 6, several of the independentelements have been combined into a configuration of an electrosurgicalprobe including porous active electrode 390, which may but need notinclude a gas-liberating alloy, to enhance the oxy-hydro combustionreaction process. Probe activation is enhanced by forcing elemental gas380 through the pores of active electrode 390 into the oxy-hydrocombustion zone for either quenching or maximizing heat of the oxy-hydrocombustion reaction. The pores of active electrode 390 allowmulti-variate functions, including metering, mixing and directing theelemental enriching gases to the combustion zone. This embodimentprovides improved fluid dynamics at the surface of active electrode 390,including a laminar flow of the ejecting gas or gases, more evendistribution of the gas or gases and rapid thermal quenchcharacteristics. When operated in underwater, cellular and biologicsurgical environments the embodiment of FIG. 6 provides means forimproving the combustion zone dynamic volume by preventing pressurefield variations from forcing the collapse of the gas volume andquenching the electrode, thereby preventing oxy-hydro combustion. Bysupplying a uniform gas field immediately above the active electrode thegas volume is created as much by the flowing of the pressurized gas asby the electrolysis of the salt ion solution. This lowers the net powerrequired to achieve ignition of the gas mixture and provides means foroperating at much lower power levels, until a spike of energy is appliedwhereupon a pulse of oxy-hydrogen gas is supplied to active electrode390, creating conditions for an oxy-hydro combustion reaction cascade.From this description it will become apparent to those skilled in theart that many dynamic controls can be used to govern the flow of gas inconcert with the power output delivered to the active electrode toachieve novel effects in the oxy-hydro combustion zone.

FIG. 7 view illustrates a more complete, but still somewhat idealized,summary of electrosurgical oxy-hydro combustion in a sodium chloride(NaCl) salt ion solution. In this case, sufficient RF energy is impartedto the solution such that the rate of electrolysis sustains oxy-hydrocombustion as shown by the overlaid equations on the representation ofthe physical flow-field. Active electrode 70 provides conducted RFelectrical energy to active electrode solid/fluid interface 305. As theRF energy is conducted through the salt ion solution, electrolysiscauses the accumulation of oxygen and hydrogen gases immediately aboutactive electrode 70. At active electrode solid/fluid interface 305, theRF energy is transmitted through a multi-phase environment consisting ofoxy-hydrogen gas and a fluid/fluid interface of oxy-hydrogen gas to saltion solution 304. Given a constant power output to active electrode 70the resistive heating of the active electrode material does not change.What does change is net heat transfer coefficient 303 (h₁) of the fluidimmediately surrounding the active electrode. It is known that overallheat transfer coefficients for gases are significantly lower than thoseof liquids. Thus, active electrode solid/fluid interface 305 experiencesa significantly lower heat transfer coefficient than fluid/liquidinterface 304 heat transfer coefficient 302 (h₂), while the power loadbeing applied remains constant. The consequence of this is a rapid andextreme temperature rise of the active electrode surface. As thetemperature of the active electrode surface rises it imparts this heatdirectly to the co-mingled, accumulated oxy-hydrogen gas 300 immediatelyabout the electrode, causing it to ignite and reduce itself to water andheat/light. This is the essence of the oxy-hydro electrosurgicalcombustion process. As the reaction takes place at elevated temperaturesneeded for ignition of the oxy-hydro combustion reaction and theco-mingled gases are of low density in relation to the salt-ionsolution, buoyancy forces 230 allow for escape of uncombustedoxy-hydrogen gas. This escape is further facilitated by normal fluidflow 240 in the surgical environment. Additionally, acid-base pairsformed during the initial electrolysis reaction are of greater densitythan water and therefore descend away from combustion zone 300.Artifacts of the acid-base pair's existence are visible in the acid-basepair density streak-lines 160. However, since the solution temperatureis near the boiling point of water, localized super saturation has takenplace at fluid/liquid interface 304. As the acid-base pairs move awayfrom combustion zone 300 cooling takes place, which results in a normalprecipitation of solid sodium chloride salt 165. In a flowingenvironment this precipitation may never take place within thejoint-space reservoir, but is visible in a static finite reservoircondition.

The two heat transfer coefficients 302, 303 are among the more dominantof the variables interacting with the system, determining the rate ofheat transferred to general flow-field and oxy-hydrogen gas/electrodeinterface 305. This variable is a key determinant in the ignition pointof the oxy-hydro combustion reaction because it is the determinant ofthe rate of temperature rise on the surface electrode as theoxy-hydrogen gas volume surrounds active electrode 70. Of importance isthe most likely point of ignition within oxy-hydro combustion zone 300,which is in the laminar boundary layer near the surface of activeelectrode solid/fluid interface 305. While it may be obvious that theflame front travels outward from the active electrode, what is lessobvious is how the combustion zone quenches itself both during and aftercombustion occurs, generating water vapor, in the form of steam. Thisvapor has a transient nature and coefficient of heat transfer that isgreater than either coefficient 302 or 303 and therefore can transferits heat far more effectively to the salt ion solution surrounding thetransient steam pocket at the fluid/liquid interface 304 immediatelyafter oxy-hydro combustion occurs. A corresponding volume change takesplace as the combustion reaction completes. In going from oxygen andhydrogen gas to water vapor a nearly 10× volumetric change takes place,collapsing the combustion zone volume and almost instantaneouslyquenching and condensing the transient steam products of oxy-hydrocombustion back into liquid water, which is quickly absorbed by the saltion solution. The entire process of electrolysis and combustion is thusready to begin anew.

FIG. 8 illustrates the more general case of variable chloride negativeion-based compound 400, which can be made up of any of Group I, period1-7 elements on the periodic table. In this case, a chloride based acid(XCI) acts as the throttle on the overall rate of reaction. It becomesclear how the salt component of the salt ion solution contributesprimarily to post oxy-hydro combustion solutionneutralization/buffering. Combustion zone 300 is essentially identicalin all variations of the salt ion cases, with no noticeable variation inthe production of H₂ gas. The general case illustration demonstrates howthe hydrolyzed Group I ion 306 participates in the stoichiometry ofelectrolysis. Acid density streak-lines 160 are still visible, ashydrochloric acid production is a normal byproduct of oxy-hydrocombustion. By understanding the underlying physiochemistry, multiplepossible configurations for salts become possible, including but notlimited to calcium-chloride salt ion solutions, magnesium-bromide saltion solutions, magnesium-iodide salt ion solutions, potassium-iodidesalt ion solutions, potassium-chloride salt ion solutions,lithium-bromide salt ion solutions, and lithium-chloride salt ionsolutions.

Other useful combinations will become apparent to those skilled in artfrom the disclosures above for additional salt ion solutions that willprovide the necessary elements for oxy-hydro combustion. To demonstratethe general case a simple mixture of hydrochloric acid was prepared inwater and a typical electrosurgical probe immersed and fired. Bubbling200 was noted as in FIG. 8 and an oxy-hydro combustion zone 300 wascreated and sustained for several minutes.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described devices,reactants and/or operating conditions of this invention for those usedin the preceding examples.

Although the invention has been described in detail with particularreference to these preferred embodiments, other embodiments can achievethe same results. Variations and modifications of the present inventionwill be obvious to those skilled in the art and it is intended to coverin the appended claims all such modifications and equivalents. Theentire disclosures of all references, applications, patents, andpublications cited above are hereby incorporated by reference.

1. A method of performing an electrosurgical procedure on a patient, the method comprising: providing a surgical probe including an active electrode and a return electrode separated by an insulator; providing an aqueous salt ion environment at the location wherein the electrosurgical procedure is to be performed, the environment comprising sufficient volume to permit immersion of at least the portion of the surgical probe including the active electrode and return electrode; and applying current to a circuit comprising the active electrode and return electrode, the current being less than that required to induce plasma ionization, but sufficient to induce electrolysis of a portion of the aqueous salt ion environment, thereby producing hydrogen and oxygen, and to further initiate a hydrogen and oxygen combustion reaction.
 2. The method of claim 1, wherein the active electrode further comprises an alloy that induces release of hydrogen.
 3. The method of claim 2, wherein the alloy is a member selected from the group consisting of a magnesium alloy and a rare earth metal and nickel alloy.
 4. The method of claim 1, wherein the aqueous salt ion environment comprises a salt ion selected from the group consisting of sodium chloride, calcium chloride, magnesium bromide, magnesium iodide, potassium iodide, potassium chloride, lithium bromide and lithium chloride.
 5. The method of claim 1, wherein the current applied comprises a high frequency voltage difference.
 6. The method of claim 5, wherein the high frequency voltage difference applied comprises radiofrequency (RF) energy.
 7. The method of claim 1, wherein the insulator comprises an electrical and thermal insulator.
 8. The method of claim 1, wherein the aqueous salt ion environment comprises naturally occurring biological fluids of the patient.
 9. The method of claim 1, wherein the aqueous salt ion environment comprises an exogenous aqueous salt ion solution.
 10. A method for inducing a therapeutic response in living tissue while minimizing deleterious acid-base shifts in the living tissue, the method comprising: providing a probe including an active electrode and a return electrode separated by an insulator, the active electrode being disposed within an elongated lumen; providing an aqueous salt ion solution at the site wherein the therapeutic response is desired, the solution comprising sufficient volume to permit immersion of at least the portion of the probe including the active electrode disposed within an elongated lumen and the return electrode; positioning the active electrode in close proximity to the location wherein the therapeutic response is desired, the active electrode and return electrode being immersed in the aqueous salt ion solution; and applying a high frequency voltage between the active electrode and return electrode, the voltage being less than that required to induce plasma ionization.
 11. The method of claim 10, wherein acid-base shifts resulting from application of the high frequency voltage are partially contained within the lumen.
 12. The method of claim 10, wherein the active electrode and return electrode separated by an insulator are disposed within the elongated lumen.
 13. The method of claim 10, wherein the position of the active electrode along the long axis of the lumen is adjustable.
 14. The method of claim 13, further comprising controlling the desired therapeutic response by adjusting the position of the active electrode along the long axis of the lumen.
 15. The method of claim 10, wherein minimal tissue necrosis is induced at the site wherein the therapeutic response is desired.
 16. The method of claim 10, wherein the active electrode further comprises an alloy that induces release of hydrogen.
 17. The method of claim 16, wherein the alloy is a member selected from the group consisting of a magnesium alloy and a rare earth metal and nickel alloy.
 18. The method of claim 10, wherein the aqueous salt ion solution comprises a salt ion selected from the group consisting of sodium chloride, calcium chloride, magnesium bromide, magnesium iodide, potassium iodide, potassium chloride, lithium bromide and lithium chloride.
 19. The method of claim 10, wherein the high frequency voltage comprises radiofrequency (RF) energy.
 20. The method of claim 10, wherein the insulator comprises an electrical and thermal insulator.
 21. The method of claim 10, wherein the therapeutic response comprises a member selected from the group consisting of nerve ablation, tissue ablation, tissue cutting, tissue coagulation, tissue modification, and induction of host healing response.
 22. A method for decreasing tissue necrosis at a site wherein high frequency voltage is applied to an active electrode immersed in an aqueous salt ion solution, the method comprising the steps of: providing an active electrode movably disposed along the long axis within an elongated lumen; immersing the active electrode in an aqueous salt ion solution; and applying a high frequency voltage to the active electrode; wherein the active electrode movably disclosed along the long axis within the elongated lumen defines a plenum chamber, the method further comprising minimizing the acid-base shift at the site by varying the volume of the plenum chamber by adjusting the position of the active electrode along the long axis of the lumen.
 23. The method of claim 22, further comprising the step of adjusting the active electrode position along the long axis such that the acid-base shift at the site does not cause deleterious alterations in tissue at the site.
 24. The method of claim 22, wherein high frequency voltage less than that required to induce plasma ionization is applied. 